Box 1: Test results in a 68-year-old woman with Powassan encephalitis
TestResult (reference range)*
Hemoglobin, g/L124 (118–151)
Mean corpuscular volume, fL89.0 (84.0–98.0))
Platelet count, × 109/L185 (147–375)
Leukocyte count, × 109/L8.6 (3.1–9.7)
Absolute neutrophil count, × 109/L6.5 (1.2–6.0)
Lymphocyte count, × 109/L0.9 (0.6–3.1)
Monocyte count, × 109/L1.1 (0.2–0.9)
Cerebrospinal fluid leukocyte count, × 106/L31 (0–5)
Cerebrospinal fluid lymphocytes, %89
Cerebrospinal fluid glucose, mmol/L3.0 (2.2–3.9)
Cerebrospinal fluid protein, g/L1.05 (0.12–0.60)
Herpes simplex virus nucleic acid testNegative
Varicella–zoster virus nucleic acid testNegative
Enterovirus nucleic acid testNegative
Mumps nucleic acid testNegative
Measles nucleic acid testNegative
Coxiella burnetii antibody testNegative
Rickettsia rickettsii antibody testNegative
West Nile virus nucleic acid test, IgM, IgGNegative, negative, negative
Cytomegalovirus IgM, IgGNegative, negative
Epstein–Barr virus IgM, IgGNegative, negative
Bartonella henselae antibody testNegative
Borrelia burgdorferi antibody testNegative
Treponema pallidum antibody testNegative
Powassan virus hemagglutination inhibition test
 Convalescent (day 30)Positive at 1:160
Powassan virus plaque reduction neutralization test
 Initial (day 0)Positive at 1:320
Convalescent (day 8)Positive at 1:5120
  • Note: IgG = immunoglobulin G, IgM = immunoglobulin M.

  • * If applicable.